56 I. BEKENBLUM AND N. TRAININ 



beeenblum: It depends what you mean by immediate. If you irradiate a cell or a group 

 of cells and transplant them, and if they remain alive, the postulated virus may develop 

 later in the surviving cells within the new host. I don't see any theoretical difficulty from 

 that point. Of course the question of the formation of new virus or provirus de novo, 

 one's attitude to that depends on whether one is brought up as a chemist or a biologist. 

 To a chemist, it is acceptable; to a bacteriologist, it appears unacceptable. Are we not 

 starting the old Pasteur argument all over again? One could imaguie that there is some 

 factor aheady present which is a "pro-pro virus" and that X-rays convert that entity 

 mto some product which urethane further converts into something else, and the final 

 entity is a virus which produces leukaemia. Whether the substance right at the beginning 

 is cliromosomal material in the chemical sense or a sort of sub-hving entity in the bacter- 

 iological sense — that is a very abstract sort of reasoning that hardly affects the argument 

 at all. One can't say C57BL have no leukaemia virus. What one can say is that using the 

 available techniques it is not normally demonstrable. 



gray: Well, one could conceive an experiment for instance m which you made your cell- 

 free extract from the in vitro irradiated material immediately. You might simply have 

 chemically transformed some RNA or DNA for that matter. 



BERENBLUM : Yes. But we have been proceeding one step at a time, and are only now 

 approaching the stage of analysing the "transmissible factor" in terms of DNA or RNA. 



